The US Secret Service has investigated an alleged death threat against Democrat Barack Obama that was yelled out on Monday at a rally for his Republican rival John McCain and running mate Sarah Palin. The probe by the service that protects US presidents, past and present, visiting world leaders and US presidential candidates, stems from a report by The Washington Post about a shout, “kill him,” heard during the rally when Obama’s name came up. The alleged threat was made when Palin was speaking of Obama’s relations with former 1960s radical Bill Ayers, whose group “The Weathermen” carried out a...